How to Use ULN2003PCB: Examples, Pinouts, and Specs

The ULN2003PCB is a printed circuit board (PCB) that integrates the ULN2003 Darlington transistor array, manufactured by JJY. The ULN2003 is a high-voltage, high-current driver IC designed to interface low-power control signals with high-power loads. The PCB simplifies the use of the ULN2003 by providing a pre-assembled, ready-to-use module with convenient pin headers for easy connection.

• Driving stepper motors in robotics and automation systems
• Controlling relays for home automation or industrial applications
• Switching high-power LEDs or lamps
• Driving solenoids in vending machines or locking mechanisms
• Interfacing microcontrollers (e.g., Arduino, Raspberry Pi) with high-power devices

• Manufacturer: JJY
• Part ID: ULN2003PCB
• Input Voltage: 3.3V to 5V (logic level inputs)
• Output Voltage: Up to 50V (load side)
• Output Current: Up to 500mA per channel (maximum total current: 2.5A)
• Number of Channels: 7 (independent Darlington transistor drivers)
• PCB Dimensions: Approximately 40mm x 20mm
• Connector Type: 10-pin header for inputs and outputs
• Integrated Features: Flyback diodes for inductive load protection

The ULN2003PCB has a 10-pin header for easy interfacing. The pin configuration is as follows:

The PCB also includes a 7-pin output terminal block for connecting the load. Each output corresponds to one of the input channels (OUT1 to OUT7).

1. Power the Module:

   • Connect the VCC pin to a 3.3V or 5V power source (depending on your control signal voltage).
   • Connect the GND pin to the ground of your power supply.

2. Connect the Inputs:

   • Use the IN1 to IN7 pins to provide control signals from a microcontroller or other logic circuit.
   • A HIGH signal (3.3V or 5V) on an input pin will activate the corresponding output channel.

3. Connect the Outputs:

   • Attach your load (e.g., motor, relay, lamp) to the corresponding output pin (OUT1 to OUT7).
   • Ensure the load's power supply is connected to the COM pin to enable flyback diode protection.

4. Verify Connections:

   • Double-check all connections to ensure proper wiring and avoid short circuits.

5. Test the Circuit:

   • Power on the system and send control signals to the input pins to activate the desired output channels.

• Flyback Diode Protection: The ULN2003 includes built-in flyback diodes to protect against voltage spikes from inductive loads. Always connect the COM pin to the positive terminal of the load's power supply.
• Current Limitations: Do not exceed 500mA per channel or 2.5A total current across all channels. Use external transistors or relays for higher current loads.
• Heat Dissipation: For high-current applications, ensure adequate ventilation or heat sinking to prevent overheating.
• Logic Level Compatibility: Ensure the input signals match the logic level of the module (3.3V or 5V).

Below is an example of how to control a 5V relay using the ULN2003PCB and an Arduino UNO:

// Example: Controlling a relay with ULN2003PCB and Arduino UNO

// Define the input pin connected to ULN2003PCB
const int relayControlPin = 7; // Connect to IN1 on ULN2003PCB

void setup() {
  pinMode(relayControlPin, OUTPUT); // Set the pin as an output
}

void loop() {
  digitalWrite(relayControlPin, HIGH); // Turn on the relay
  delay(1000); // Wait for 1 second
  digitalWrite(relayControlPin, LOW);  // Turn off the relay
  delay(1000); // Wait for 1 second
}

1. No Output on Load Side:

   • Cause: Incorrect wiring or missing power connections.
   • Solution: Verify that the VCC, GND, and COM pins are properly connected. Ensure the input signal is HIGH (3.3V or 5V).

2. Overheating of the Module:

   • Cause: Exceeding the current rating of the ULN2003.
   • Solution: Reduce the load current or use external relays/transistors for high-power devices.

3. Inductive Load Not Working Properly:

   • Cause: Flyback diode protection not enabled.
   • Solution: Ensure the COM pin is connected to the positive terminal of the load's power supply.

4. Microcontroller Resetting or Malfunctioning:

   • Cause: Voltage spikes or noise from the load.
   • Solution: Use decoupling capacitors near the microcontroller and ensure proper grounding.

• Q: Can I use the ULN2003PCB with a 12V motor?
  A: Yes, as long as the motor's current does not exceed 500mA per channel. Connect the motor's power supply to the COM pin.

• Q: Is the ULN2003PCB compatible with 3.3V logic?
  A: Yes, the module works with both 3.3V and 5V logic levels.

• Q: Can I control multiple loads simultaneously?
  A: Yes, you can control up to 7 loads, provided the total current does not exceed 2.5A.

• Q: Do I need external diodes for inductive loads?
  A: No, the ULN2003 includes built-in flyback diodes for this purpose.

This concludes the documentation for the ULN2003PCB.